This guide covers Mozilla Thunderbird 115 (Supernova) and Thunderbird 128 (Nebula). Thunderbird 128 introduced a redesigned interface, but the account setup process is the same in both versions.

What you will need

• Your full email address (e.g. you@yourdomain.com)
• Your email password
• Your mail server hostname — find this in cPanel under Email Accounts → Connect Devices. It is typically mail.yourdomain.com.

Add the account

1. Open Thunderbird.
2. Click the three-line menu button in the top-right corner.
3. Go to New → Existing Email Account.
4. Fill in the setup form:
   • Your full name: the display name for outgoing messages
   • Email address: your full email address
   • Password: your email password
5. Click Continue. Thunderbird will attempt to auto-detect the server settings using the domain part of your address.

If auto-detect succeeds

If Thunderbird finds IMAP — mail.yourdomain.com — port 993 — SSL/TLS for incoming and SMTP — mail.yourdomain.com — port 465 — SSL/TLS for outgoing, the settings are correct. Click Done to finish.

If auto-detect fails or finds incorrect settings

1. Click Configure manually (below the detected results).
2. Set the incoming (IMAP) settings:
   • Protocol: IMAP
   • Server: mail.yourdomain.com
   • Port: 993
   • Connection security: SSL/TLS
   • Authentication method: Normal password
   • Username: your full email address
3. Set the outgoing (SMTP) settings:
   • Server: mail.yourdomain.com
   • Port: 465
   • Connection security: SSL/TLS
   • Authentication method: Normal password
   • Username: your full email address
4. Click Re-test to verify the connection.
5. Click Done.

Certificate warning — what it means and when to accept

If Thunderbird shows a certificate warning that mentions a hostname such as server123.tpc-hosting.com instead of your domain name, this is normal behavior on shared hosting. The SSL certificate is issued for the server hostname, not your individual domain. You can safely click Confirm Security Exception to proceed. The connection is still encrypted — only the certificate name differs from your domain name.

Troubleshooting

• If port 465 is rejected, try SMTP port 587 with STARTTLS security.
• Confirm the exact server hostname in cPanel: Email Accounts → Connect Devices.
• If Thunderbird shows authentication errors, verify that the username is set to your full email address (not just the part before the @).